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10

Worm Wheel Moulding.

place by removing top box, form gates and vents, and complete
casting.

A Worm Wheel may have a pattern made in halves, and be
moulded in an exactly similar manner (see Fig. 12); the teeth on

the pattern being formed so as to gear with a wrought iron
worm which has been previously turned, the worm and wheel
pattern being rigged up on two axles to imitate their condition
when in actual work. In withdrawing the pattern from the sand
a slight screw motion must be given to allow for the angle of the
teeth.

Moulding boxes are entirely or to some extent dispensed with,
and the floor of the foundry used for the reception of the pattern
wherever convenient; and then, except in such cases as that
shewn in Fig. 4, a cope or slab of sand is used, contained in a
box, to cover the impression. Examples of this kind of moulding,
with more or less complicated copes, will now be treated.

Fig. 13 is the plan of a Drilling Machine Table. The
pattern is of the same shape, with the exception of core prints
necessary for the slot holes. A core box is required for these
holes, and the whole is moulded face down, an extra piece being
ijeft in the casting at top, if thought necessary, to allow for scum.
Instead of the bottom box the floor might have been used, if
previously well vented with coke.

Perhaps the most ready way to mould the Cylinder Cover
shewn in Figs, 15 and 16 is to use three boxes (or what really comes